This invention relates to a system and method for obtaining samples of oil from an oil system of an electrical power device, such as a power transformer, a load tap changer and the like.
Active components of an electrical power device, such as a transformer, handle rather high electrical current that can cause arcing and/or over heating in an air environment. Oil systems have generally been employed to provide a relatively oxygen free environment and to cool the active components. A typical oil system contains a volume of oil and a tank in which the active component is submerged in oil. The tank generally includes a top fill valve and a bottom drain valve.
Abnormal operation of the power transformer can be detected by the analysis of gases and moisture contained in oil samples taken from the oil system at periodic intervals. This detection allows appropriate action to be taken that prevents serious damage to the power transformer. ASTM Designation: D 3613-92 describes a method for obtaining oil samples. This method obtains the sample from the bottom drain valve of the tank. This method has several drawbacks. The bottom drain valve is connected to the bottom of the tank, which is a dead zone or inactive region for the oil. Active regions for the oil are those in which the oil has contact with the active component and becomes heated. As the drain valve region is below the active component, the oil therein is not representative of the oil in the system. Sediment settles to the bottom region. For this reason, the method requires that the drain valve drain an initial volume of about two quarts of oil into a flush container to remove any effects of the sediment. Thereafter, the oil sampling device is connected with the drain valve and another quantity of about one quart of oil is passed through the sampling device into the flush container to assure a bubble free sample is obtained. The method requires that an oil flush container be used and that the flush oil be disposed of according to good environmental practice.
Thus, there is a need for an oil sampling system and method for obtaining a representative oil sample without handling a flush container and a disposition of flush oil.
The oil sampling system of the present invention provides the above mentioned need with a closed loop sampling of the oil of an electrical power device. An oil containing apparatus includes a tank in which a component of the electrical power device is submerged in oil. A sampling device is removably connected with first and second ports of the oil containing apparatus so that oil flows through the sampling device in a closed loop with the oil containing apparatus. The first port is located to receive a flow of oil from an active region of the oil containing apparatus.
In transformer embodiments, the second port is vertically displaced downwardly from the first port so that oil flows through the sampling device aided by cooling of the oil and gravity. In one embodiment, the first port is connected to a top fill valve of the tank and the second port is connected to a bottom drain valve of the tank. In other embodiments, the first port is connected to a top header pipe of a radiator of the oil containing apparatus. The second port is connected with a bottom header pipe of the radiator.
In another embodiment, a pump circulates the oil through the closed loop in which the sampling device is removably connected.
The method of the present invention begins with connecting the oil sampling device in the closed loop. The oil is passed through the sampling device. The sampling device is then disconnected with a quantity of oil for analysis. The oil is taken up from an upper active region of the oil containing apparatus so as to obtain a representative oil sample without the need for a flush container or flushing operation.
In one embodiment of the invention, a new sampling device is installed in the closed loop after an old sampling device is removed. This procedure assures that a sample is always available.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.